Grbl-lpc, grbl-stm running on non-standard boards

Anyone managed to run grbl-lpc on SKR and/or any other LPC1768/9 based controllers other than grbl “supported” boards? And what about grbl-stm?

How do you manually map pins to match that of your boards?
I would like to try out grbl with lightburn but the more i search for how to install and configure it, the more i see how messy it can be for non-standard boards - if possible at all.

It took me only couple of hours to replace a M2Nano with SKR 1.3 running smoothie cluster and for things to work great. reading about grbl fw does not make me feel it’s going to be as easy.